Media Prep, Isolation

Question 1

General steps in culture media preparation

Answer 1

• Weighing of dehydrated media or media
  ingredients
• Dissolving of components in the solvent
• Checking/adjustment of pH (optional)
• Dispensing into glassware/containers
• Capping or plugging with cotton
• Sterilization (usually at 15 psi for 15 minutes)

Question 2

an axenic culture -
culture that contains only one group of
microorganisms which is usually obtained
when microorganisms in a culture medium
are all of the same specie

Answer 2

pure culture

Question 3

Instruments used to maintain pure culture

Answer 3

pipette
Inoculating needles and loops

Question 4

an instrument often used to transfer aliquots of culture, to prepare serial dilutions of microorganisms, and to dispense chemical agents

Answer 4

pipette

Question 5

used to aseptically transfer
microorganisms from broth, slant, or agar cultures to other media

Answer 5

Inoculating needles and loops

Question 6

set of specific practices and procedures performed under
carefully controlled conditions with the goal of minimizing contamination

Answer 6

Aseptic techniques

Question 7

Pure Culture Techniques:

Answer 7

Enrichment Culture
Membrane Filter Technique
Plating Techniques

Question 8

• isolation of specific types of microorganisms by a
  combination of nutrient and physical conditions

Answer 8

Enrichment Culture

Question 9

for samples with low population (pure culture technique)

Answer 9

Membrane Filter Technique

Question 10

Plating techniques:

Answer 10

Pour Plate Method/Culture
Spread Plate Method/Culture
Streak Plate Method/Culture

Question 11

measured by following changes in the number of
cells or weight of cells

Answer 11

Measurement of Growth

Question 12

Measurement of Growth:

Answer 12

1. direct methods
2. indirect methods

Question 13

direct methods in the measurement of microbial cell growth:

Answer 13

• direct microscopic count: total cell count
• standard plate count (viable cell count) and serial dilution
• most probable number (MPN)

Question 14

indirect methods in the measurement of microbial cell growth:

Answer 14

• turbidity measurement
• metabolic activity
• total weight measurement

Question 15

can be used as a direct method to determine the number of bacterial cells in a culture or liquid medium.
In this procedure, the number of cells in a given volume of culture liquid is counted directly in 10-20 microscope fields.

Answer 15

Petroff-Hausser Chamber

Question 16

Particles are held in suspension in a dilute electrolyte which is drawn through the orifice with a voltage applied across it.
. Voltage pulse is recorded as particles flow through the orifice.
* Amplitude of pulse can be related to volume of particle.

Answer 16

Coulter Counter (Electrozone Sensing method)